Electric heating apparatus



F. L. BISHOP.-

ELECTRIC HEATING APPARATUS.

APPLICATION FILED MAR. 16. 1916.

1,321,504. Patented Nov. 1]., 1919.

F. L. BISHOP. ELECTRIC HEATING APPARATUS. APPLICATION FILED MAR. 16. I916.

Patented Nov. 11, 1919.

3 SHEETS-SHEET 2.

VENTOR F. LQBISHOP. ELECTRIC HEATING APPARATUS.

APPLICATION FILED MAR. I6. I916. Patented NOV 11 3 SHEETSSHEE[ 3.

. filed February 26,

809,831, filed January 2,1914, the present application being,

FREDERIG BISHOP, OF PITTSBURGH, PENNSYLVANIA.

ELECTRIC HEATING AIPIPARATUS.

Specification 01. Letters Patent. Patented NOV. 11, 1919.

Application filed March 16, 1916.- Serial No. 84,664.

To all whom it may concern:

Be it known that I, FREDERIC L. BISHOP, a citizen. of the United States, residing at Pittsburgh, in'the county of Allegheny and State 'of Pennsylvania, have invented certain new and useful Improvements in Electric Heating Apparatus, of which the fol-- lowing is a full, clear, and exact description, reference being had to the-accompanying drawings, forming part of this specification, in which t Figure 1 is a vertical section showing one form of apparatus embodying my invention.

Fig. 2 is a section, on the line II-II, of Fig. l.

Fig. 3 is a wiring diagram showing coils, circuits, and one form of current regulator.

Fig. 4 is a detail view showing a part of the current regulator.

Fig. 5 is a vertical section illustrating a quenching tank which may be employed,

- and r Fig. 6 is a view similar to Fig. 1, but

showing the heater adapted for another purpose.

My invention has relation to electric heating apparatus, which has been-more particularly designed for use for the purpose of treating metal, particularly iron and steel, for the purpose of altering its molecular structure, as described and claimed in my copending applications, Serial No. 750,844, 1913, and Serial No.

in part, a division of said application Serial No. 809,831.

The present invention has particular reference to electric heating means of novel character which is adapted to utilize the heating action produced by the action of the magnetic field of an alternating electric current.

My invention provides heating apparatus of this character which is not only adapted .to the treatment of metal placed within its magnetic field, but may also be used for heat-' ing others-ubstances.

I will first describe my invention with particular relation to the heat treatment of metal.

Referring to the accompanying drawings, the numeral 2 designates a suitable case or closure, preferably constructed of heat insulating material, and within which the metal objects indicated at A and B are designed to.be placed while being subjected to the novel treatment. shown in Figs. 1 and 2 is designed for the treatment of two pieces of metal simultaneously. For'this purpose I provide within the casing or closure 2, two hollow coils v These coils have withm them a lining 4 of non-conducting 3, placed side by side.

material such as clay, terra cotta or mica. I also preferably place within the linings 4 a metal lining 5 which serves to protect the linings 4 from direct contact with the metal. This inner shell 5 may be in the form of a closed cylinder, in which induced eddy currents will circulate, as shown at the left hand side of Fig. 2; or it maybe dividedinto segments, as shown at the right hand side of Fig. 2, to prevent the circulation of induced electric currents therein. The magnetic circuits of the coils or wind ings 3 is completed through the metallichead block 6, which is preferably laminated as shown; and when the apparatus is in use it is placed over a suitable pit or other support containing a base block 7 of mag- The apparatus net-ic material. The lower ends of the 1101- low coils are arranged to be closed by means of doors 8 having removable pivots 9 and arranged to be held closed by. means of suitable latch devices 10. Each of the coils or windings 3 is preferably composed of a I number of separate coils 3, as shown in Fig. 3. These co1ls are arranged to receive current from an alternating generator 11 through a current regulating switch 12 by means of which the coils may be connected 1n variousways. The terminals of the several coils 3 are connected to the series of relatively fixed contact fingers 13 which are arranged tobe engaged by a series of movable contacts 14. This movable contact member is shown as having five positions with respect to the contacts 13, namely, the open circuit position in which the parts are shown in Fig. 3, and the positions indicated by the several dotted lines a, a, b, b,

c, c, d, d; ,the position (1, d being an open circuit position. Without tracing out the circuits of the coils in detail in the several positions of the current regulating switch,

it Wlll be readily seen that in the position -a, a all the coils will be connected in parallel; that in the posltion b, bthe two upper coils will be connected in series with each -other and in parallel with the two lower coils; and that in the position 0, c all four coils will be connected in series.

It is desirable to make use of the changes in the magnetic properties of the metal being treated to automatically control the heating operation and to cut ofi the current when the desired treatment is complete. F or this purpose it is necessary to provide the member of the current regulating switch which carries the movable contacts 13 with an actuating device capable of effecting a step by step movement of said member as the current in the circuit of the coils 3 changes. This may be accomplished in various ways. In the current regulator shown in Figs. 3 and 1, the member carrying the contacts 14 is arranged to be moved laterally with respect to the contacts 13 and is connected to a movable plunger 15. This plunger at its opposite end extends within the closed receptacle 16 designed to be partially filled with oil or other suitable liquid, and carries therein a piston composed of a plurality of separated plates 17. These plates are provided with perforations 18 adapted to permit of a relatively slow circulation of the oil therethrough. The piston is provided with a series of teeth or notches 19 for engagement with a pivoted dog 20 which forms the armature of an electromagnet 21 which is connected in series in the supply circuit for the coils. The armature dog 20 has a lever arm 22 connected thereto and carries an adjustable counterweight 23. The armature dog 20 is arranged to hold the rod or plunger 15 against the action of a counterweight 24 connected thereto.

The operation is as follows:

The metal objects A and B to be treated a're first set upon the doors 8, which have 'been detached from the apparatus by the removal of the pivots 9. The casing or closure 2 is (by a crane or any other suitable means) brought over the said metal objects and dropped over them so that they are inclosed within the coils, or windings in the manner shown in Figs. 1 and 2. The

pins 9 are then inserted and the doors are secured by the latches 10. The entire apparatus is then moved over the pit or other support shown in Fig. 1 and placed in such position thereon that the base block 7 of magnetic material is directly below the pieces A and B. The necessary circuit connections for the coils are then established and the current regulating switch is manually moved to the position indicated by the dotted line a, a. The several coils 3 of each Winding remain connected in parallel until the metal is preferably heated to a temperature near the recalescence point of the metal. At this time the changes in the magnetic properties of the metal tend from its engagement with the rod or plunger 15. The counterweight 24 now acts to remove said rod or plunger against the action of the oil in the receptacle 16 and a total distance substantiallv equal to the distance between adjacent notches or teeth of said plunger where it is stopped by the resistance of the oil. This connects the coils 3 in series-parallel, thus increasing their resistance and cutting down the flow of current proportionately to such increase. This weakens the magnet 21, and the armature dog now drops into engagement. with the next tooth or notch.

As the temperature of the pieces A and B continues to increase, a further increase in current takes place in the circuit of the said coils, resulting in another step movement of the regulator and so on until the proper treatment has been given to the metal when the circuit is opened by the regulator.

In this manner the proper limit of temperature is not only automatically indicated, but the current is automatically shut off and heating beyond such temperature is prevented. It will be understood, however, that for certain purposes the predetermined temperature may be other than that above described. That is to say, the device may 100 be so adjusted that it will shut oil? the current before the recalescence point is reached, if this should be desirable in any particular case. In some instances it is desirable to shut off the current when a temperature 05 just below the recalescence point is reached. Inasmuch as the current flow has commenced to increase materially at some degrees below the recalescence point, the regulating device can be readily set so as to cut 110 off the current fiow after the current increase commences and before its maximum flow is reached. In some cases also it may be desirable to carry the heating beyond the recalescence point and beyond the tempera- 115 turc at which the metal, loses its magnetic properties. In such cases, the regulating device is simply S0 adjusted that it will not trip at the recalescence point but the current will remain on until shut off by other 1 0 means. In such case the coils 3 may be used as resistance units and the material heated directly from said coils, instead of by the action of the currents induced in the metal.

After the treatment is completed, the apparatus may be l'OIl'lOVOAl from the pit or other support and carried over a quenching tank containing the quenchin liquid. The bottom doors 8 can then be released and the 130 -ment thereof having perforated lateralk walls. his inner .compartment may be made of any desiredarea in cross sectionrelative to the cross-sectional area of the piece being treated, and thereby (in the manner of a dash-pot) regulating the time required for the piece to become immersed therein. The cooling can be further regulated by the size of the perforations in the wall of the compartment.

The tank 25 should be provided with a heavy bottom 27 sufficiently strong to stand the shocks when the pieces are dropped suddenly thereon.

The heating above described being also of'a uniform character, very exact results in annealing and tempering of the metal can be obtained and these results can be accurately reproduced in successive pieces.

In some cases, however, it may be desired to slowly cool the treated metal while still under the action of the magnetic field. This can be readily effected by properly controlling the current in the heating coils.

By employing an inner shell or lining 5 of a character to permitthe circulation of induced currents therein, such shell or lining may be very quickly heated and may be made to impart heat directly to the metal objects. I preferably employ an alternating current of about sixty cycles for the production of the varying magnetic field, but do not limit myself in this respect.

In Fig. 6 I have shown the apparatus arranged for the heating of water. In this figure the same numerals are employed to designate corresponding parts as in Fig. 1, with the suffix a.

In this apparatus the metal pieces A and B are replaced by the liquid containers C and D, one of these containers having an inlet connection E, the other an outlet con-. nection F, and the two containers having a bottom circulating connection G. In this form of my invention the action isthe same as in the form first described, except that the material to be heated is a liquid within a magnetic field. In this, form of my invention it is not necessary that there shall be any automatic regulation of the current, al-

though this can be readily accomplished by a, thermostatic means of Well known character.

- It will be obvious that in this manner, water, or other liquids may be heated, or various other heating operations may be carried out. The form of the apparatus may, of course, be varied to suit the particular objector materials being heated. Instead of being arranged to treattwo pieces at once, the a paratus may be arranged to treat a sing e piece, or more than two pieces. The general construction and arrangement of .the parts may be widely varied, the number of sections or units of the coils may be changed; other forms of current regulating switches may be em ployed, and various other changes may be 1. Apparatus of the character described,

comprising a hollow coil or winding adapted to inclose an article to be treated, said coil or winding being composed of a plurality of sections, a regulating switch to which said sections are connected, and means controlled by the flow of current through the sections for automatically operating said switch to connect the sections in different relations, substantially as described.

2. Apparatus of the character described, comprising a hollow coilor winding, means for supplying electric current thereto, and pieces of magnetic material adjacent to the ends of the coil or winding, the coil or. winding'being movable with respect to one of the end pieces, substantially as described.

3. Apparatus of the character described, comprising a hollow Vertical coil or winding, pieces of magnetic material adjacent to the ends of said coil or winding, said coil or winding being movable toward and away from one of said pieces, substantially as described.

4;. Apparatus of the character described, comprising a hollow coil or winding adapted to inclose a metal object to be subjected to the magnetic field thereof, and movable door means closing one end of said coil or -w inding, substantially as described.

movable together as a unit, substantially as described.

.7. Apparatus of the character described,

comprising a hollow coil or Winding adapted to inclose the object or substance to be heated, and switch means controlled by changes in the properties of such object or substance for automatically controlling the current supplied to said coil, substantially as described.

8. Apparatus of the character described, comprising a hollow coil or Winding, a source of alternating current connected thereto, and means whereby changes in the properties of the material being treated are caused to automatically indicate When a predetermined heating temperature has been reached, substantially as described.

9. Apparatus of the character described, comprising a coil or Winding adapted to contain therein a piece of metal to be heated, a source of alternating current connected to said coil or Winding, and means Whereby chan 'es in the magnetic properties of the metfi being heated are caused to automatically control such supply of current, substantially as described.

In testimony whereof, I have hereunto set my hand.

I FREDERIC L. BISHOP.

Witnesses:

J. HAMMOND SMITH, L. H. HARRIS. 

